JP2007187030A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device capable of suppressing variation of fuel injection amount among cylinders. <P>SOLUTION: A first check valve 11 allowing passage of fuel from a high pressure fuel channel 4 to a channel open and close part 5a and a second check valve 12 allowing passage of fuel from the channel open and close part 5a to the high pressure fuel channel 4 are provided between the high pressure fuel channel 4 and the channel open and close part 5a of a fuel injection valve 5 for each cylinder, and a volume chamber 13 storing fuel is provided between the check valves 11, 12 and the channel open and close part 5a. Valve open pressure difference of the first check valve 11 is set lower than valve open pressure difference of the second check valve 12, the valve open pressure of the second check valve 12 is set higher than pressure drop in the high pressure fuel channel 4 generated when a small quantity of fuel is injected at low pressure from one of fuel injection valves 5, and lower than pressure drop in the high pressure fuel channel 4 generated when a large quantity of fuel is injected at high pressure from the injection valves 5. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection device that injects fuel discharged from a high-pressure pump having a pressure adjusting mechanism from a fuel injection valve for each cylinder.

As a fuel injection device for an internal combustion engine, the fuel in the fuel tank is pressurized to a feed pressure with a low-pressure electric pump, and the fuel is further pressurized with a high-pressure pump driven by the internal combustion engine and supplied to the common rail, which is connected to the common rail. A device that injects fuel by opening and closing a fuel injection valve for each cylinder has been put to practical use. In this type of fuel injection device, a pressure adjustment mechanism is added to the high-pressure pump, and when the amount of fuel to be injected from the fuel injection valve is small, the fuel pressure in the common rail is controlled to a low pressure region, and when the amount of fuel is large, the common rail By controlling the fuel pressure in the high pressure region, the dynamic range of the injection amount is expanded. Patent Documents 1 to 5 exist as prior art documents related to the present invention.
JP 2001-140733 A Japanese Patent Laid-Open No. 9-184460 JP 2001-82282 A JP-A-8-189445 JP 11-182380 A

  In the conventional fuel injection device described above, the pumping of the common rail fuel from the high pressure pump may be limited to one time for fuel injection to a plurality of cylinders (for example, two cylinders). When such a pump operation is performed, the pressure in the common rail is reduced by the fuel injection to the first cylinder after the fuel is pumped, and the fuel injection pressure differs between the cylinders. For this reason, the fuel injection amount varies among the cylinders particularly at the time of low pressure small amount injection. As a solution to such a problem, there is a method in which fuel is pumped from a high-pressure pump to a common rail every time fuel is injected into each cylinder. However, it may be difficult to operate the pump at such a high frequency due to the operation limit of the high-pressure pump. In addition, measures may be taken to reduce the fuel pressure by increasing the volume of the common rail, but as the volume increases, the pressure increase speed of the fuel pressure in the common rail decreases and the responsiveness of the fuel pressure deteriorates. There is a fear. The above-described fuel injection devices of Patent Documents 1 to 5 do not have an effective solution for such a problem.

  An object of the present invention is to provide a fuel injection device capable of suppressing variations in fuel injection amount between cylinders during low-pressure small-quantity injection by means different from the conventional one.

  The present invention has a configuration in which fuel discharged from a high-pressure pump provided with a pressure adjusting mechanism is distributed to each fuel injection valve for each cylinder via a fuel flow path shared between the cylinders. When the fuel injection amount from the engine is set to a small amount region, the fuel injection pressure is set to a low pressure region, and when the fuel injection amount is set to a large amount region, the fuel injection pressure is set to a high pressure region. In the fuel injection device for injecting fuel from the fuel injection valve by opening / closing a flow path opening / closing portion provided in each fuel injection valve while operating the pressure adjusting mechanism to be set, Between each of the fuel injection valves, the fuel is allowed to pass from the fuel flow path to the flow path opening / closing section, and the fuel flow from the flow path opening / closing section to the fuel flow path is allowed. A first check valve for blocking the flow, and the fuel from the flow path opening / closing portion. A second check valve that allows fuel to pass through the flow path and blocks the flow of fuel from the fuel flow path to the flow path opening / closing section; the first check valve; and the second check valve A volume chamber for storing fuel between the stop valve and the flow path opening / closing portion, and the valve opening differential pressure of the first check valve is greater than the valve opening differential pressure of the second check valve The valve opening differential pressure of the second check valve is smaller than the amount of pressure drop in the fuel flow path that occurs when fuel is injected from the fuel injection valve of any one cylinder in the small amount region. The above-mentioned problem is solved by setting the fuel flow rate to be large and smaller than the pressure drop amount of the fuel flow path when fuel is injected from the fuel injection valve of the one cylinder in the large quantity region. ).

  According to the fuel injection device of the present invention, by sending fuel from the high pressure pump to the fuel flow path, the first check valve corresponding to each fuel injection valve is opened by the fuel pressure, and the fuel pressure is applied to each volume chamber. Is stored. When fuel is injected from the fuel injection valve of one of the cylinders in this state, the pressure in the fuel flow path decreases according to the amount of fuel injection. At this time, when the fuel injection amount is set in the small amount region, the amount of pressure drop in the fuel flow path stops in a range smaller than the valve opening differential pressure of the second check valve, so the second check valve is Do not open. For this reason, the initial pressure is held in the volume chamber connected to the fuel injection valve other than the fuel injection valve that has performed the fuel injection. Therefore, even if no pressure is supplied from the high-pressure pump before fuel injection to the next cylinder, the fuel injection valve of the next cylinder uses the pressure in the volume chamber to inject an appropriate amount of fuel at an appropriate injection pressure. Can do. As a result, variations in the fuel injection amount among the cylinders when the injection pressure is low and the fuel injection amount is set in the small amount range are suppressed. On the other hand, when the fuel injection amount is set to a large amount region, the pressure drop amount of the fuel flow path accompanying the fuel injection with respect to any one cylinder becomes larger than the valve opening differential pressure of the second check valve. As a result, the pressure of the fuel stored in the volume chamber corresponding to the other fuel injection valve acts on the fuel injection valve that performs the fuel injection, and the reduction of the injection pressure is prevented. That is, at the time of high pressure mass injection, fuel injection to each cylinder can be performed using the pressures of all the volume chambers. Thereby, the dispersion | variation between the cylinders of the fuel injection quantity at the time of a high pressure large quantity injection does not deteriorate.

  In one form of the fuel injection device of the present invention, the discharge cycle of the high pressure pump is set so that the fuel is pumped once from the high pressure pump to the fuel flow path each time fuel is injected into a plurality of cylinders. (Claim 2). Even when the discharge cycle of the high-pressure pump is set in this way, the injection pressure at the time of fuel injection to each cylinder is maintained equally as described above.

  Furthermore, in one form of the fuel injection device of the present invention, the second check valve is opened with respect to an increase in the pressure in the volume chamber due to the stop of the operation of the engine to which the fuel injection device is applied. A valve opening differential pressure of the second check valve may be set (Claim 3). According to this aspect, it is possible to eliminate the possibility that the fuel pressure in the volume chamber will rise excessively after the engine is stopped.

  As described above, according to the fuel injection device of the present invention, when a small amount of fuel is injected from the fuel injection valve at a low pressure, the second check valve corresponding to the other fuel injection valve is closed and the volume is closed. Since the fuel pressure is maintained in the room, even if the pressure of the fuel flow path shared between the cylinders decreases as the fuel is injected into one of the cylinders, the fuel is maintained at an appropriate pressure for the other cylinders. Can be injected, thereby suppressing variations in the fuel injection amount among the cylinders. On the other hand, when a large amount of fuel is injected from the fuel injection valve, the second check valve is opened to inject fuel into each cylinder using the pressure in all the volume chambers. In addition, variation in the fuel injection amount among the cylinders can be suppressed.

  FIG. 1 shows an embodiment in which the fuel injection device of the present invention is applied to a four-cylinder direct injection internal combustion engine (hereinafter referred to as an engine). However, the illustration of the engine is omitted. The fuel injection device 1 includes a fuel supply device 3 that pressurizes and sends fuel stored in a fuel tank 2, a high-pressure fuel passage 4 through which the fuel sent from the fuel supply device 3 is guided, and the high-pressure fuel passage. And a fuel injection valve 5 for injecting fuel distributed from 4 into the cylinder. The high pressure fuel flow path 4 is shared between the cylinders. One fuel injection valve 5 is provided for each cylinder. In FIG. 1, cylinder numbers # 1 to # 4 are assigned to the fuel injection valve 5 to show the correspondence with the cylinders. The high-pressure fuel flow path 4 may be any one that can distribute fuel to each fuel injection valve 5, and the volume thereof may be smaller than the volume of the common rail provided in the conventional fuel injection device.

  The fuel supply device 3 pumps up the fuel in the fuel tank 2 and pressurizes it to the feed pressure, and sends it to the low-pressure fuel flow path 7 and further pressurizes the fuel in the low-pressure fuel flow path 7 to increase the pressure of the high-pressure fuel flow path. 4 is provided with a high-pressure pump 8 to be fed to the vehicle 4. The low pressure pump 6 is driven at a constant speed by an electric motor. On the other hand, the high-pressure pump 8 is mechanically driven by using a rotational motion taken out from a drive shaft (crankshaft) of the engine. As an example, the high-pressure pump 8 is a plunger-type pump that converts the rotational movement of the drive shaft of the engine into the reciprocating movement of the plunger by a cam mechanism and repeats the fuel intake operation and the pushing-out operation using the plunger reciprocating movement. Composed. The fuel discharge period of the high-pressure pump 8 is set so that the fuel is discharged once for fuel injection from the fuel injection valve 5 into the two cylinders. The high pressure pump 8 includes a pressure adjusting mechanism 8a. As an example, the pressure adjusting mechanism 8a changes the throttle amount of the flow path for taking fuel from the low pressure fuel flow path 7 into the high pressure pump 8, thereby changing the pressure of the fuel discharged from the high pressure pump 8 to a predetermined value. The pressure is varied between a low pressure region and a high pressure region within the pressure adjustment range. The high pressure fuel flow path 4 is provided with a pressure adjusting valve 9 that limits the maximum pressure inside the high pressure fuel flow path 4 and a pressure sensor 10 that detects the fuel pressure in the high pressure fuel flow path 4. The fuel discharged from the pressure regulating valve 9 is returned to the low pressure fuel flow path 7.

  The fuel injection valve 5 opens and closes the internal flow path by opening and closing a flow path opening / closing section 5a provided therein, and injects fuel guided from the high-pressure fuel flow path 4 into the cylinder. The flow path opening / closing section 5a may be any as long as it can open and close the internal flow path leading to the injection hole of the fuel injection valve 5. As an example, the flow path opening / closing part 5a is configured as an electromagnetic valve that opens and closes an internal flow path by driving a valve body by excitation of a solenoid coil. In order to keep the pressure of the fuel guided from the high-pressure fuel flow path 4 to the flow path opening / closing section 5a properly, a first reverse is provided between the high-pressure fuel flow path 4 and the flow path opening / closing section 5a of each fuel injection valve 5. A stop valve 11 and a second check valve 12 and a volume chamber 13 for storing fuel are provided between the first check valve 11 and the second check valve 12 and the flow path opening / closing part 5a. ing.

  The first check valve 11 allows the fuel to pass from the high pressure fuel flow path 4 to the flow path opening / closing part 5a and blocks the flow of fuel from the flow path opening / closing part 5a to the high pressure fuel flow path 4. On the other hand, the second check valve 12 allows the fuel to pass from the flow path opening / closing part 5a to the high pressure fuel flow path 4 and blocks the flow of fuel from the high pressure fuel flow path 4 to the flow path opening / closing part 5a. . The valve opening differential pressure (cracking pressure) of the check valves 11 and 12 will be described later. The volume chamber 13 is provided to store a pressure for injecting fuel from the fuel injection valve 5 in place of the common rail of the conventional fuel injection device. The volume of the volume chamber 13 is set to a value obtained by dividing the volume of the conventional common rail by the number of cylinders of the engine. That is, the volume of the conventional common rail is evenly distributed to each volume chamber 13. However, if the high-pressure fuel flow path 4 has a volume that cannot be ignored, the remaining volume obtained by subtracting the volume of the high-pressure fuel flow path 4 from the volume of the conventional common rail is equally distributed to each volume chamber 13. Good.

  The operations of the pressure adjusting mechanism 8a of the high pressure pump 8 and the flow path opening / closing portion 5a of the fuel injection valve 5 are controlled by an electronic control unit (ECU) 15. The ECU 15 calculates the amount of fuel to be injected from the fuel injection valve 5 (target injection amount) according to the operating state of the engine, and according to the calculated target injection amount, The valve opening time (on-duty ratio) is controlled via the electronic drive unit (EDU) 16, and the discharge pressure of the high-pressure pump 8 is changed between the low-pressure region and the high-pressure region according to the fuel injection amount. When the target injection amount is set in a small range within the adjustment range, the ECU 15 adjusts the pressure of the fuel discharged from the high pressure pump 8 to the high pressure fuel flow path 4 so as to be set in a predetermined low pressure range. To operate. On the other hand, when the target injection amount is set to a large amount within the adjustment range, the ECU 15 adjusts the pressure so that the pressure of the fuel discharged from the high pressure pump 8 to the high pressure fuel flow path 4 is set to a predetermined high pressure range. The mechanism 8a is operated. By performing such an operation, the ECU 15 functions as a fuel pressure control unit that adjusts the fuel pressure in accordance with the fuel injection amount.

  Further, the valve opening differential pressures of the first check valve 11 and the second check valve 12 are set as follows. First, when the valve opening differential pressure of the first check valve 11 is ΔPa and the valve opening differential pressure of the second check valve is ΔPb, ΔPa <ΔPb, that is, the valve opening differential pressure ΔPa. Is set smaller than the valve opening differential pressure ΔPb. Next, regarding the valve opening differential pressure ΔPb of the second check valve 12, the amount of pressure drop in the high-pressure fuel flow path 4 that occurs when fuel is injected from the fuel injection valve 5 of any one cylinder in a small amount region. And a pressure drop amount of the high-pressure fuel flow path 4 generated when fuel is injected from the fuel injection valve 5 of any one of the cylinders in a large amount region. As described above, in the fuel injection device 1 of the present embodiment, the fuel discharge operation of the high-pressure pump 8 is set to discharge the fuel once for the fuel injection to the two cylinders. Therefore, after fuel is discharged from the high-pressure pump 8, when fuel is injected into the first cylinder, the fuel pressure in the high-pressure fuel flow path 4 decreases accordingly. The amount of pressure drop when injecting fuel in a small amount region is small, and the amount of pressure drop is large when injecting fuel in a large amount region. The valve opening differential pressure of the second check valve 12 is set so that whether or not the valve is opened is switched according to the amount of the pressure drop. That is, the valve opening differential pressure of the second check valve 12 is set so that it does not open when a small amount of fuel is injected in the low pressure region and opens when a large amount of fuel is injected in the high pressure region. Yes.

  Next, the operation of the fuel injection device 1 will be described with reference to FIG. In the following, the fuel injection order from the fuel injection valve 5 is in the order of # 1 → # 3 → # 4 → # 2 → # 1. When the high-pressure pump 8 is started as the engine starts, the fuel discharged from the high-pressure pump 8 is guided to the high-pressure fuel flow path 4, and the first check valve 11 is opened by the pressure to open each cylinder. The fuel pressure is stored in the volume chamber 13. At this time, all the second check valves 12 are kept closed. If fuel is injected from any one of the fuel injection valves 5 (here, assumed to be the # 1 fuel injection valve 5) from this state, the pressure is high until the fuel injection from the # 3 fuel injection valve 5 is performed. Since fuel is not discharged from the pump 8, the fuel pressure in the high-pressure fuel flow path 4 is reduced by an amount corresponding to the fuel injection amount (see part A in FIG. 2). At this time, if the fuel injection amount is set in the small amount region, the pressure drop amount is smaller than the valve opening differential pressure of the second check valve 12, and therefore the fuel injection of # 3 to be injected next The second check valve 12 corresponding to the valve 5 does not open, and the initial pressure is maintained in the volume chamber 13 leading to the # 3 fuel injection valve 5 (see part B in FIG. 2). Accordingly, the fuel injection pressure from the # 3 fuel injection valve 5 is maintained equal to the fuel injection pressure from the # 1 fuel injection valve 5. After the fuel is injected from the # 3 fuel injection valve 5, the fuel pressure in the high pressure fuel flow path 4 and each volume chamber 13 is recovered by supplying the fuel from the high pressure pump 8 (see arrow C in FIG. 2). ). Accordingly, the fuel injection pressure from the # 4 fuel injection valve 5 and the fuel injection pressure from the # 2 fuel injection valve 5 are also maintained at the same level as the fuel injection pressure from the # 1 fuel injection valve 5. As a result, the variation in the fuel injection amount between the cylinders at the time of the low-pressure small-quantity injection is suppressed as compared with that of the fuel injection device using the conventional common rail.

  On the other hand, when the fuel injection amount from the # 1 fuel injection valve 5 is set to a large amount region, the pressure drop amount of the high-pressure fuel flow path 4 accompanying the fuel injection from the # 1 fuel injection valve 5 is the second. It becomes larger than the valve opening differential pressure of the check valve 12. As a result, the second check valves 12 corresponding to the fuel injection valves 5 of # 2 to # 4 are all opened. As a result, the pressure in the volume chamber 13 corresponding to the # 2 to # 4 fuel injection valves 5 acts on the # 1 fuel injection valve 5 via the high-pressure fuel flow path 4, thereby preventing a decrease in the injection pressure. Similarly, when the fuel is injected from the # 3 fuel injection valve 5 in a large quantity region, the pressure in the volume chamber 13 corresponding to the other fuel injection valve 5 acts on the # 3 fuel injection valve 5 in the same manner. A drop in the injection pressure is prevented. That is, since all the volume chambers 13 are used as high-pressure volumes for supplying pressure to each fuel injection valve 5 at the time of high-pressure mass injection, variations in the fuel injection amount among the cylinders are caused by fuel injection using a conventional common rail. Equivalent to the equipment.

  According to the fuel injection device 1 of the present embodiment, when the engine stops and the fuel temperature rises, and the fuel pressure rises accordingly, the second check valve opens and the fuel pressure becomes high. The valve opening differential pressure of the second check valve 12 is set so as to be released to the fuel flow path 4. Thereby, the possibility that the fuel pressure in the volume chamber 13 rises excessively can be eliminated.

  The present invention is not limited to the form described above, and may be implemented in various forms. For example, the engine to which the present invention is applied is not limited to four cylinders, and can be applied to engines having other numbers of cylinders. The present invention is not limited to the in-cylinder injection engine, but can be applied to a port injection engine. 1, the first check valve 11, the second check valve 12, and the volume chamber 13 are provided as parts different from the fuel injection valve 5. However, all or a part of these are provided as fuel injection valves. 5 may be incorporated. In short, the first check valve, the second check valve, and the volume between the fuel flow path shared between the cylinders and the flow path opening / closing portion of the fuel injection valve that is opened and closed for fuel injection. It is sufficient that the room exists. The check valve may have any function as long as it has a function of opening and closing a flow path in one direction according to the valve opening differential pressure and preventing the flow in the opposite direction.

The figure which shows the 4-cylinder engine to which the fuel-injection apparatus of this invention was applied. The figure which shows the change of the fuel pressure in each fuel injection valve with respect to the fuel injection from each fuel injection valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 3 Fuel supply apparatus 4 High pressure fuel flow path 5 Fuel injection valve 5a Flow path opening / closing part 6 Low pressure pump 7 Low pressure fuel flow path 8 High pressure pump 8a Pressure adjustment mechanism 11 First check valve 12 Second check Valve 13 Volume chamber

Claims (3)

The fuel injection from the fuel injection valve has a configuration in which fuel discharged from a high-pressure pump having a pressure adjusting mechanism is distributed to each fuel injection valve for each cylinder via a fuel flow path shared between the cylinders. The fuel injection pressure is set to a low pressure region when the amount is set to a small amount region, and the fuel injection pressure is set to a high pressure region when the fuel injection amount is set to a large amount region. In the fuel injection device for injecting fuel from the fuel injection valve by opening / closing a flow path opening / closing portion provided in each fuel injection valve while operating the pressure adjusting mechanism,
Between the fuel flow path and each flow path opening / closing part of the fuel injection valve, fuel is allowed to pass from the fuel flow path to the flow path opening / closing part, and the fuel flow from the flow path opening / closing part. A first check valve for blocking fuel flow to the passage, and the passage of fuel from the flow path opening / closing section to the fuel flow path, and the flow of fuel from the fuel flow path to the flow path opening / closing section A second check valve for blocking the flow, and a volume chamber for storing fuel between the first check valve and the second check valve and the flow path opening and closing unit,
The valve opening differential pressure of the first check valve is set smaller than the valve opening differential pressure of the second check valve;
The valve opening differential pressure of the second check valve is larger than a pressure drop amount of the fuel flow path generated when fuel is injected from the fuel injection valve of any one of the cylinders in the small amount region, and It is set smaller than the pressure drop amount of the fuel flow path when fuel is injected from the fuel injection valve of one cylinder in the large quantity region,
The fuel-injection apparatus characterized by the above-mentioned.   The discharge cycle of the high pressure pump is set so that the fuel is pumped once from the high pressure pump to the fuel flow path each time fuel is injected into a plurality of cylinders. Fuel injectors.   The valve opening differential pressure of the second check valve is set so that the second check valve opens with respect to the pressure increase in the volume chamber due to the stop of the operation of the engine to which the fuel injection device is applied. The fuel injection device according to claim 1, wherein the fuel injection device is provided.

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